1. Field of the Invention
The present invention relates to a washing machine, and more particularly, to a washing machine with a vibration-preventing structure for preventing the transfer of the vibration of the driving part to other part, thereby minimizing occurrence of vibration and noise.
2. Discussion of the Related Art
Generally, washing machine is an apparatus for washing laundry using frictional action of wash water, emulsification action of detergent and so forth. The wash procedure of the washing machine generally includes cycles of wash, rinse and dehydration.
In these washing machines, an outer tub containing wash water is fixedly installed inside a cabinet appearance of a washing machine, a washing tub for receiving the laundry is rotatably installed inside the outer tub, and a driving part for rotating the washing tub is installed below the outer tub.
Hereinafter, the structure of the driving part is described with reference to FIGS. 1 and 2.
FIG. 1 is a sectional view of a driving part of a conventional washing machine, and FIG. 2 is a sectional vie taken along the line I-I of FIG. 1.
As shown in FIG. 1, a tub base 2 for supporting an outer tub 1 is installed at the lower portion of the outer tub 1, and a bearing housing 10 is installed at the lower portion of the tub base 2.
A stator 3 is installed at the lower portion of the bearing housing 10, and a rotor 5 is rotatably installed outside the stator 3. The rotor 5 is fixed to a rotor housing 50. The rotor 5 is maintained spaced apart from the stator 3 at a constant interval, e.g., approximately 0.5 mm. In other words, the driving part shown in FIG. 1 is an outer rotor type induction motor.
A hollow washing tub shaft 20 is rotatably installed inside the bearing housing 10. Inside the washing tub shaft 20 is installed a decelerator 40. An upper pulsator shaft 33 is connected to an upper portion of the decelerator 40 and a lower pulsator shaft 31 is connected to a lower portion of the decelerator 40. At this time, the upper end of the washing tub shaft 20 is coupled to the washing tub (not shown), and the upper end of the upper pulsator shaft 33 is coupled to the pulsator (not shown).
A rotor bushing 60 is coupled to the core of the rotor housing 50, and the lower end of the lower pulsator shaft 31 penetrates the rotor bushing 60 and is coupled thereto. The rotor bushing 60 is fixed to the rotor housing 50 by a plurality of coupling bolts 65.
In order to transfer the rotational force of the lower pulsator shaft 31 to the washing tub shaft 20, a coupling 70 is installed at the outer circumference of the washing tub shaft 20 and the outer circumference of the rotor bushing 60. According to the location of the coupling 70, the washing tub shaft 20 is selectively coupled to the rotor bushing 60, and during their coupling, the rotational force of the lower pulsator shaft 31 is transferred to the washing tub shaft 20.
As shown in FIG. 2, a coupling part 61 having a polygonal section is formed at the inner circumference of the rotor bushing 60. The coupling part 61 is coupled to the outer circumference of the lower pulsator shaft 31 to transfer the rotational force of the rotor housing 50 to the lower pulsator shaft 31. Also, a serration part 63 is formed at the outer circumference of the rotor bushing 60. Through the serration part 63, the coupling 70 ascends and descends, and the lower pulsator shaft 31 and the washing tub shaft 20 are coupled or separated depending on the location of the coupling 70.
Meanwhile, as shown in FIG. 1, between the bearing housing 10 and the washing tub shaft 20, and between the washing tub shaft 20 and the pulsator shaft 31, 33 are installed a plurality of bearings 11, 13.
However, the driving part of the conventional washing machine may cause the following problems. In other words, since the rotor 5 is a rotational body, it always generates some vibration. Then, since the rotor housing 50 is directly coupled to the pulsator shaft 31, 33 or the washing tub shaft 20 through the rotor bushing 60, the vibration of the rotor 5 is transferred without any filtering. In this case, the vibration of the rotor 5 is transferred to the washing tub or the outer tub 1, so that a considerable noise is caused.
In particular, the rotor 5 does not rotate at a constant revolution per minute (RPM) but is driven while varying the RPM within a certain range. Owing to the variation of the RPM, there occurs a ripple phenomenon in which the pulsator shaft 31,33 or the washing tub shaft 20 vibrates. For instance, if the rotor 5 is set to rotate at an 850 rpm, it rotates in real in a range of 840-860 rpm. At this time, the ripple phenomenon is one vibration source, which is directly transferred to the washing tub or the outer tub 1 to cause a regular noise during its operation.